The present invention relates generally to a fuel injection control device for use with an internal combustion engine for determining the fuel injection amount supplied to the engine based on various engine operation parameters such as engine load, engine speed and/or engine temperature. More particularly, the invention relates to a fuel injection control device with an improved start-up characteristic.
An electronically-controlled fuel injection control device determines a fuel injection amount corresponding to engine operating conditions defined by various engine operation parameters such as, for example, engine load, engine speed, and/or engine temperature. Further, the fuel injection control device corrects the determined fuel injection amount based on the correction parameters for the engine.
The fuel injection devices presently in use inject a predetermined fuel amount once per each revolution of the engine. Fuel injection is effected to all the engine cylinders at the same timing when a reference position pulse is supplied which is output every time the engine crank shaft revolves over a predetermined angle.
For this reason, in the worst case, it may take 360.degree. with respect to the crank angle from the beginning of cranking at start-up of the engine until the fuel injection device calculates the fuel injection amount to thereby actually inject the fuel.
Reference is made, for instance, to a 4-cycle, 6-cylinder reciprocating engine having a sensor for detecting a crank shaft angle position. The sensor outputs a reference position pulse for each given crank angle of 120.degree. (corresponding to an interval of combustion of engine). As shown in FIG. 1, at time T.sub.1, cranking starts and after time T.sub.1, a reference position pulse No. 1 is generated. Thereafter, whenever the crank shaft revolves over 120.degree., reference position pulses No. 2, No. 3 . . . are successively generated. In the event that the fuel injection device injects fuel once per each revolution, whenever three reference position pulses are input, i.e. every crank shaft revolving angle of 360.degree., fuel injection is effected.
In the above example, if cranking begins at T.sub.1 fuel injection cannot be effected until the reference position pulse No. 3 is produced. The engine thus starts after reference pulse No. 3 is produced, which results in prolonging the cranking time.
The prolonged or delayed time of fuel injection is in fact merely from a tenth of a second to a few seconds. However, drivers feel that the cranking time is relatively long giving an impression of a bad start-up characteristic.